JP3080624U - Laser barcode scanner signal processor - Google Patents

Abstract

(57) [Problem] In a conventional bar code reader, a difference in the distance to a bar code affects the amount of reflected light, and the magnitude of the obtained signal causes the electric circuit to become saturated or erroneous reading. This causes a problem that the resolution and reading range of the barcode are limited. According to the present invention, when a bar code signal obtained from a light receiving element is pre-amplified, a previously amplified and output bar code signal is fed back to the light emitting diode.
b, emit light, receive light with the light-sensitive resistor 11a, control the gain of the amplifier 15 of the automatic gain control unit 1 with the resistance value at that time, change the amplification factor, and change the barcode signal obtained from the light-receiving element. Provided is a signal processing device of a laser barcode scanner that properly amplifies and performs signal processing in a subsequent stage.

Description

[Detailed description of the invention]

[0001]

[Technical field to which the invention belongs]

 The present invention relates to a signal processing device for a laser barcode scanner, and particularly to a barcode signal obtained by a light receiving element, which is appropriately amplified and transmitted to a subsequent processing unit by an automatic gain control method. The present invention relates to a signal processing device for a laser barcode scanner (hereinafter, referred to as a barcode reader).

[0002]

[Prior art]

 In general,

[0003]

[Prior art and its problems]

 In general, a non-contact bar code reader that uses laser light irradiates the bar code with laser light from a laser emitting element, captures the light reflected by the bar code, and directly emits light by photoelectric conversion. After being converted into an electric signal (barcode signal), the signal is amplified to a level that can be processed by an amplifier circuit, and further input to a digital conversion circuit to be digitized. The digitized barcode signal is decoded by a decoding circuit.

[0004]

[Problems to be solved by the invention]

 In such a barcode reading device, a user usually does not determine a distance to a barcode to be read within a readable distance, that is, does not read at a fixed distance. The difference in the distance to the bar code causes a difference in the energy amount of the laser beam reaching the bar code, and also causes a difference in the energy amount of the reflected light reflected and captured by the bar code. The distance between the code reader and the bar code affects the reading result.

That is, since the signal level detected by the light receiving sensor is affected by the amount of energy of the reflected light, if the gain of the amplifier circuit is fixed, the signal level detected by the light receiving sensor is If the signal level is too large, the electric circuit will be saturated.On the other hand, if the signal level is too low, the signal will not be amplified to a level sufficient for processing, or it will be susceptible to noise, etc. There is a problem that the resolution of the bar code and the readable range are limited.

[0006] Therefore, in order to solve the above-described problem, the present invention has a circuit configuration using an automatic gain control method equipped with a gain adjustment element controlled based on the output of a light emitting element, and has an appropriate gain. It is an object of the present invention to provide a signal processing device of a laser barcode scanner which performs control and does not limit the resolution of a barcode and a readable range.

[0007]

[Means for Solving the Problems]

 In order to achieve the above object, the present invention irradiates a bar code with laser light and adjusts the optical characteristics of the signal in a laser bar code scanner signal processing device which reads information expressed from the reflected light. An automatic gain that includes a portion and a first signal amplifying section whose gain is adjusted according to a change in characteristics of the adjustment portion, and that prevents generation of self-vibration caused by gain by an input signal based on the reflected light. A control unit; a second signal amplification unit that amplifies an output signal from the first signal amplification unit of the automatic gain control unit to a predetermined level and outputs the signal as a barcode signal; A signal level detection unit that inputs a part of the signal amplified and output from the unit, and outputs a detection signal indicating that when the level of the signal exceeds a predetermined level; An automatic gain control voltage unit that receives a detection signal from the signal level detection unit and generates a gain control voltage value using a capacitance element and a resistance element; and buffers a gain control voltage output value output from the automatic gain control voltage unit. The present invention provides a signal processing device for a laser barcode scanner, which does not affect gain control and includes a buffer unit that supplies a gain control voltage output value to the adjustment unit of the automatic gain control unit. .

Further, an application amplifier or another component having a high resistance input and a low resistance output is used as the buffer unit. The adjustment part of the automatic gain control unit 1 includes a light-emitting element and an adjustment element whose resistance value changes according to the amount of light received. An optical element emits light, the output resistance of the adjustment element is changed according to the amount of light from the light emitting element, and the first signal amplifying section is controlled to suppress an increase or a decrease in the output of the second signal amplifying section. Control the gain.

In the signal processing device of the laser barcode scanner configured as described above, when the output barcode signal has a low level for performing signal processing, the gain control voltage value decreases, The brightness of the light emitting element in the automatic gain control unit also becomes weak, the resistance value of the adjustment element increases, and the gain of the automatic gain control unit increases, so that the level of the output bar code signal increases. The amplification ratio becomes high. On the other hand, when the level of the bar code signal increases, the gain control voltage value increases, the brightness of the light emitting element increases, the resistance value of the adjustment element decreases, and the gain of the automatic gain control unit decreases. As a result, the amplification factor becomes further lower so that the level of the output bar code signal becomes lower, and the desired amplification factor is obtained.

[0010]

[Embodiment of the invention]

 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a conceptual block configuration of a signal processing device of a laser barcode scanner (barcode reading device) according to an embodiment of the present invention, and FIG. 2 shows a circuit example of the signal processing device. . This signal processing device is a part mounted on a bar code reading device that irradiates a bar code with laser light and reads bar code information represented by the reflected light, and performs amplification processing using an automatic gain control method by feedback. , A signal (bar code signal) output from a light receiving element (not shown) that photoelectrically converts the reflected light from the bar code is appropriately amplified and output to a bar code signal processing unit (not shown) at a subsequent stage. .

As shown in FIG. 1, the signal processing device controls an amplification gain (gain) based on an output signal of a light receiving element that photoelectrically converts reflected light from a bar code, as described later. And a signal for amplifying the bar code signal output from the automatic gain control unit 1 with a fixed gain and outputting the amplified signal to a subsequent bar code signal processing unit. An amplifier 2, a part of the amplified bar code signal, and a signal level detector 3 for outputting a detection signal when the signal exceeds a predetermined reference level (reference voltage); An automatic gain control voltage unit 4 for generating a gain control voltage value based on the following formula: and a buffer unit 5 for transmitting the gain control voltage value to the automatic gain control unit 1.

The above-described components will be described in detail with reference to a circuit example shown in FIG. The automatic gain control unit 1 includes a gain adjustment unit 11 composed of a pair of a light-sensitive resistor 11a and a light-emitting diode 11b functioning as a light receiving element, a resistor 12 and a capacitor connected in parallel to both output terminals of the gain adjustment unit 11, respectively. 14 and the signal output from the power supply from the input terminal 7 and the signal output from the light receiving element from the input terminal 6 are input to the respective input terminals (+) and (−), and the signals indicated by the gain adjustment unit 11 The amplifier 15 performs preamplification. The resistor 14 connected in parallel to the photosensitive resistor 11a can prevent self-vibration that may occur when the value of the gain is adjusted.

The signal amplifying unit 2 mainly includes amplifiers 18 and 19 connected in series. The bar code signal preamplified by the automatic gain control unit 1 is amplified by the amplifiers 18 and 19 and output to the output terminal 20. . These amplifiers 18 and 19 are connected to capacitors 21 and 23 and resistors 22 and 24, respectively, and amplify the barcode signal with a fixed gain. Here, a part of the amplified barcode signal is connected to the input terminal of the signal level detection unit 3 via the capacitor 25.

The signal level detection unit 3 is mainly composed of an amplifier 26 and a plurality of resistors, and detects when the voltage value of the amplified bar code signal exceeds a reference level based on the power supply from the input terminal 7. Output a signal.

The automatic gain control voltage section 4 includes a diode 28 for inputting a detection signal to the anode side via a resistor 27, a capacitor 30 and a resistor 31 connected between the cathode of the diode 28 and the ground, A diode 29 whose anode is connected to the cathode. The automatic gain control voltage section 4 obtains a control voltage value of a required gain from the detection signal from the signal level detection section 3. The output of the automatic gain control voltage unit 4 is input to the buffer unit 5 including an operational amplifier 32 and a resistor 33. The operational amplifier 32 outputs the control voltage value of the gain to the light emitting diode 11b via the resistor 33. I do. The buffer unit 5 is used to buffer the gain control voltage value from the automatic gain control voltage unit 4 and prevents the gain control voltage value from being affected.

The automatic gain control in the signal processing device configured as described above will be described. In this automatic gain control method, first, a light receiving element of a reading device receives reflected light from a bar code, and an output signal (bar code signal) generated by photoelectric conversion is input from an input terminal 6 to the automatic gain control unit 1. The signal is input to the amplifier 15. At this time, the gain of the amplifier 15 is set based on the gain control signal (gain control signal voltage value) calculated previously. The bar code signal pre-amplified by the amplifier 15 is amplified to a required voltage level by the signal amplifying section 2 and output to a subsequent processing circuit via an output terminal 20. At this time, a part of the barcode signal output from the signal amplifying unit 2 is branched for sampling for generating a gain control signal and sent to the signal level detecting unit 3. In the signal level detector 3, when the voltage value of the bar code signal exceeds the reference level, a detection signal is output to the automatic gain control voltage unit 4 via the resistor 27.

In the automatic gain control voltage section 4, the detection signal passes through the diode 28 in the forward direction to charge the capacitor 30, and the charged voltage is used as a gain control voltage. In order to vary the gain in accordance with the level of the gain control voltage, a resistor 31 is connected in parallel to the capacitor 28, and has a path through which the charge of the capacitor 28 can be discharged. If the resistor 31 is not provided, the capacitor 30 will be charged continuously, and the accumulated voltage will be quickly saturated, possibly losing the function of adjusting the gain.

The variable gain control voltage obtained from the automatic gain control voltage section 4 is used for automatic gain control. However, when this gain control voltage is directly supplied to the light emitting diode 11b, the control voltage may be affected by the diode PN pole junction voltage characteristic and the internal resistance characteristic of the light emitting diode 11b. Therefore, an operation amplifier 32 functioning as the buffer 5 is provided. The buffer 5 may be formed of a component having a high-resistance input and a low-resistance output characteristic.

Here, the gain control of the automatic gain control unit 1 using the gain control voltage will be described. If the output signal from the light receiving element (not shown) is weak, the gain control voltage fed back also decreases, so that the light emission amount of the light emitting diode 11b decreases, the resistance value of the photosensitive resistor 11a increases, and the gain of the amplifier 15 increases. Increases, the amplification factor increases, and the voltage level of the bar code signal pre-amplified and output from the automatic gain controller 1 increases. On the other hand, if the output signal from the light receiving element is excessive, the gain control voltage fed back also increases, and the light emitting diode 11b becomes bright. Along with this, the resistance value of the photosensitive resistor 11a decreases, the gain of the amplifier 15 decreases, the amplification factor decreases, and the voltage level of the bar code signal pre-amplified and output from the automatic gain control unit 1 decreases. Become.

As described above, the light emitting diode 11b emits light at a signal level in accordance with the strength of the output signal from the light receiving element, and a change in the brightness changes the resistance value of the light-sensitive resistor 11a. To realize the control, a preferable barcode signal processing device is obtained.

In the present embodiment, the light emitting diode is used as the control means. However, the present invention is not limited to this, and it is easy to realize such gain control using a light emitting element such as a lamp. It is. Similarly, a light-sensitive resistor is used as a light-receiving element for performing gain control, but other components that cause a change in resistance or a change in voltage due to photoelectric conversion may be used. The present embodiment described above is an example, and it is easy to appropriately apply the present invention without departing from the gist of the present invention, and the configuration shown in the preferred embodiment is not an absolute limitation of the present invention.

[0022]

[Effect of the invention]

 As described above in detail, according to the present invention, an appropriate automatic gain is provided by using a circuit configuration using an automatic gain control method equipped with a gain adjustment element controlled based on the output of the light emitting element, and the bar code A signal processing device for a laser barcode scanner in which the resolution and the readable range are not limited can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration example of a signal processing device according to the present invention.

FIG. 2 is a diagram illustrating a circuit configuration of the signal processing device illustrated in FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Automatic gain control part 2 ... Signal amplification part 3 ... Signal level detection part 4 ... Automatic gain control voltage part 5 ... Buffer part

Claims (3)

[Utility model registration claims] 1. A signal processing device for a laser bar code scanner for irradiating a bar code with a laser beam and reading information expressed from the reflected light, an adjustment portion that optically changes characteristics, and a characteristic of the adjustment portion. An automatic gain control unit comprising: a first signal amplifying unit whose gain is adjusted according to a change; and an automatic gain control unit for preventing generation of self-vibration caused by a gain by an input signal based on the reflected light; A second signal amplifier that amplifies an output signal from the first signal amplifier to a predetermined level and outputs the amplified signal as a barcode signal; and a second amplifier that outputs a signal amplified and output from the second signal amplifier. A signal level detecting section for inputting a part and outputting a detection signal indicating the fact when the level of the signal exceeds a predetermined level; and detecting the signal level from the signal level detecting section. An automatic gain control voltage section that receives a signal and generates a gain control voltage value by a capacitive element and a resistive element; and buffers the gain control voltage output value output from the automatic gain control voltage section to affect the gain control. A signal processing device for a laser barcode scanner, comprising: a buffer unit for not supplying the signal to the adjusting unit of the automatic gain control unit and supplying a gain control voltage output value to the adjustment unit. 2. The signal processing device according to claim 1, wherein an application amplifier or another component having a high resistance input and a low resistance output is used as the buffer unit. 3. The adjusting portion of the automatic gain control section 1 includes a light emitting element and an adjusting element whose resistance value changes according to the amount of light received, and a time-varying gain control voltage input from the buffer section. The light emitting element emits light according to the output value, and the output resistance value of the adjustment element is changed according to the amount of light from the light emitting element. The signal processing device for a laser barcode scanner according to claim 1, wherein the gain of the signal amplifying unit is controlled.